Preliminary Ornamental Classification of Biotitic Granites from Cubal (SW of Angola)

José Vítor  Lisboa; Paulo Nuno  Caessa; Rui Pedro Lopes; Álvaro  Oliveira; Paulo Bravo Silva; Jorge Fernández; José Feliciano Rodrigues; José Manuel

doi:10.21701/bolgeomin/136.2/002

Authors

José Vítor Lisboa Laboratório Nacional de Energia e Geologia (LNEG) https://orcid.org/0000-0002-4983-9347
Paulo Nuno Caessa UTE (IGME, LNEG, Impulso Industrial Alternativo) - PLANAGEO https://orcid.org/0009-0002-1435-0266
Rui Pedro Lopes UTE (IGME, LNEG, Impulso Industrial Alternativo) - PLANAGEO https://orcid.org/0009-0006-9895-0662
Álvaro Oliveira Laboratório Nacional de Energia e Geologia (LNEG) https://orcid.org/0000-0001-8475-2485
Paulo Bravo Silva UTE (IGME, LNEG, Impulso Industrial Alternativo) - PLANAGEO https://orcid.org/0000-0001-7460-9925
Jorge Fernández Departamento de Recursos Geológicos para la Transición Ecológica, Centro Nacional Instituto Geológico y Minero de España https://orcid.org/0000-0002-3125-405X
José Feliciano Rodrigues Laboratório Nacional de Energia e Geologia (LNEG) https://orcid.org/0000-0001-8246-9379
José Manuel Instituto Geológico de Angola (IGEO) https://orcid.org/0000-0001-5509-5068

DOI:

https://doi.org/10.21701/bolgeomin/136.2/002

Keywords:

Granite, Ornamental stone, Cubal, Potential, Classification

Abstract

In the Cubal region between Benguela and Huambo (SW of Angola), grey biotite granites of middle Paleoproterozoic age occur on a planation surface as residual reliefs, either of inselberg or inselgbirge type. The objective of this work is to carry out the preliminary classification of the grey granites of the Cubal region (SW of Angola), ranking the areas in relation to their potential in granites as ornamental rocks. Six granite lithotypes were identified, which can be grouped into 3 sets according to their textural characteristics. The petrographic analysis reveals that from a mineralogical point of view, granitic lithotypes are very similar with a significant content of plagioclase. The samples chemical analysis shows a homogeneous acidic composition in the granite composition range. Tests were carried out to determine real and apparent density, total and open porosity, water absorption at atmospheric pressure, compressive strength, and bending strength. The results show that the Cubal granites have the characteristics of quality ornamental stones, which in general can be used in all types of applications, in interior and exterior environments. Based on a set of variables, an empirical classification of the ornamental potential of the granites was made, where 4 levels of increasing potential in the study area are established.

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